Magnetic parts, each including a core made of a soft magnetic material such as iron or an alloy of iron and a coil placed around the core, have been utilized in various fields. A dust core made of a green compact is an example of the above core (see PTL 1). The green compact is typically manufactured by filling a compacting space, which is defined by a die having a through hole and a lower punch disposed so as to cover one opening portion of the through hole of the die, with a raw-material powder, pressurizing the raw-material powder using the lower punch and an upper punch, and then removing the green compact from the die. A thermally-treated material, which is obtained by subjecting the green compact to a thermal treatment, is normally utilized as a core.
In the case where the magnetic parts are used in an alternating-current magnetic field, a core having a low iron loss (approximately the sum of hysteresis loss and eddy current loss) is desired. Particularly, since high eddy current loss occurs in a core that is used at high frequencies, such as several kHz or higher, it is desirable that the core having reduced eddy current loss. As described in Patent Literature 1, if a coated soft magnetic powder, which is constituted by coated particles each obtained by coating an outer circumference of a metal particle, made of a soft magnetic material such as an iron particle, with an insulating coated film (insulating layer), is adopted as a raw-material powder, the electrical resistance of a green compact can be increased with the metal particles being insulated from each other. Thus, if this green compact is adopted as a core, a low-loss core that can effectively reduce eddy current loss can be obtained.